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In mechanical applications, defect-based fatigue cracking is a significant strength-limiting failure mode of additively manufactured composites that is not yet fully understood in the service environment. In this paper, axial loading tests were carried out at 25 ℃ and 450 ℃, and then the effects of temperature on the long-life fatigue properties of the TiC-reinforced Ti6Al4V composite fabricated by Laser Powder Bed Fusion (LPBF) were investigated by combining the techniques of electron backscatter diffraction, X-ray computed tomography, and 3D morphological reconstruction. With the increase in temperature, the fatigue strength of the LPBF TiC/Ti6Al4V composite decreases significantly. The main causes of the interior failure at both temperatures are the inhomogeneous hardening zone (IHZ) formed by TiC agglomeration and the pore defect generated during the manufacturing process. The presence of brittle IHZ and pores causes stress concentration, which leads to crack nucleation. When a crack reaches the specimen surface, the combined effects of temperature and oxygen accelerate the ensuing crack propagation at high temperature. Based on the temperature effect, material properties, and the statistical distribution of defects, a model has been developed to predict the P-S-N curves at both temperatures. This model performed well in estimating the fatigue strength at 109 cycles. These findings provide new insights into the defect-related fatigue failure mechanisms and strength evaluation of the LPBF TiC/Ti6Al4V composite at different temperatures. [Display omitted] • Two defect-based cracking modes with IMZ-fisheye are revealed. • One cracking is attributed to the aggregation and debonding of TiC particles. • The other cracking is due to the irregular pores formed during LPBF. • A strength evaluation model with statistical defect size is proposed. [ABSTRACT FROM AUTHOR]

Reactive materials are functional structural materials that balance structural strength and reactivity, and their shock response is greatly influenced by the characteristics of reactive components. This article aims at understanding the shock compression and reaction of Al-Hf reactive materials with two values of the Al-Hf particle size ratio α (1 µm:10 µm and 10 µm:10 µm), which were prepared through hot pressing with a compactness (the ratio of density to theoretical maximum density) greater than 96.46%. The free surface velocity of the materials was measured in the impact velocity range of 279–865 m/s. The Hugoniot elastic limit (HEL), spall strength, and Hugoniot relationships under shock stresses of 1.83–14.46 GPa were analyzed on the basis of the microstructure and phase change. Continuous Al phase was formed in the sample with α = 0.1, while more Hf–Hf contact and crushed Hf appeared in the sample with α = 1. The velocity profiles presented clear signs of the linear growth to the HEL, the slow increase to the peak, and the subsequent pullback, indicating the transition from elastic to plastic and spall behavior. The HEL fluctuated significantly with increasing shock stress, while the spall strength first increased and then decreased. The sample with a continuous Al phase exhibited a lower HEL (0.52–0.97 GPa) and higher spall strength (0.31–0.46 GPa). The microstructure had a significant effect on the shock induced chemical reaction of the materials. Shock velocity was linearly related to particle velocity for the α = 0.1 sample, while a notable quadratic growth was observed for the α = 1 sample owing to self-reactions under the lower shock stress (5.32 GPa). The intermetallic Hf 4 Al 3 observed in the recovered product by X-ray diffraction further verified the phenomenon. • Nearly fully dense Al-Hf reactive material was prepared by hot pressing. • The effect of microstructure on the shock behaviors and reaction characteristics was investigated. • The sample with larger particle size of Al exhibited higher Hugoniot elastic limit and lower spall strength. • Intermetallic Al 4 Hf 3 was observed in the recovered samples, and sample with larger Al are more prone to reactions. [ABSTRACT FROM AUTHOR]

The silver nanowires (Ag NWs) prepared by improved polyol method in 30min were applied to the stretchable strain sensors. Three factors affecting the morphology of Ag NWs were discussed, including reaction temperature, molecular weight of PVP, ratio of silver nitrate (AgNO 3) and polyvinyl pyrrolidone (PVP). Experimental results showed that Ag NWs with diameter of 53 ± 9 nm, length of 31 ± 7 μm and the aspect ratio is 584.9 were obtained under the optimum conditions. Thus, a new and convenient method was proposed to fabricate flexible stretchable sensors by embed Ag NWs into Polydimethylsiloxane (PDMS). The stability, hysteresis, and sensitivity of the Ag NWs@PDMS strain sensors were evaluated by cyclic stretch-release test. Our strain sensor with good stability, higher sensitivity (the gauge factor is 4.11) and good repeatability could be stretched 10% continuously for about 200 cycles. Ag NWs@PDMS flexible sensors can be used in wearable devices to monitor human movements. Image 1 • The effects of different conditions on the morphology of silver nanowires were discussed based on the rapid polyol method. • We propose a novel method to prepare Ag NWs@PDMS flexible stretching sensor. • The sensitivity, hysteresis and repeatability of the sensor are studied. • Ag NWs@PDMS flexible sensors are assembled at the knees to monitor human movement. [ABSTRACT FROM AUTHOR]

Abstract Different content of Ti4+ has been successfully doped into the lattice sites of Cr3+ in NaCrO 2 by the two step solid-state reaction. The analysis results of crystal structure demonstrate that the interslab (NaO 2) spacing is increased with Ti doping content, which contributes to widening the sodium ion migration channel and then facilitating the rapid (de)intercalation capability of sodium ions. During charge-discharge processes, these O3-Na 1-x Cr 1-x Ti x O 2 (x = 0.03, 0.05, 0.1) layered oxides exhibit delayed O3-P3 phase transition and increased average discharge voltage due to stronger Ti-O bond relative to Cr-O bond. In particular, the Na 0.95 Cr 0.95 Ti 0.05 O 2 shows the optimal electrochemical performance which releases a discharge specific capacity of 96.7 mAh g−1 at 1 C (100 mA g−1) with 80.1% capacity retention after 800 cycles. Even under the high rate of 30 C, it can deliver a discharge specific capacity of 67 mAh g−1. Highlights • The sodium ion migration channel of NaCrO 2 was widened by Ti doping. • The Ti-doped NaCrO 2 exhibited delayed O3-P3 phase transition and increased average discharge voltage. • The Na 0.95 Cr 0.95 Ti 0.05 O 2 displayed an excellent rate capability and cycling capability. [ABSTRACT FROM AUTHOR]

Abstract With the aim of improving the strength and ductility of TiAl alloy, for the first time, nano-WC is introduced to reinforce the Ti-44.5Al-5Nb-0.5W-0.5C-0.2B through hot isostatic pressing (HIP). The effect of nano-WC contents on the microstructures and mechanical properties of Ti-44.5Al-5Nb-0.5W-0.5C-0.2B are systematically studied, specifically, the Ti-44.5Al-5Nb-0.5W-0.5C-0.2B alloy with 2 wt% nano-WC content shows the highest tensile strength (830 ± 33 MPa) and ductility (3.9 ± 0.2%), which are mainly attributed to the grain refinement strengthening and precipitate shearing strengthening effects. Our findings provide a realistic approach to design novel TiAl/WC nanocomposite processed by HIP with superior strength-ductility combination for practical structural applications. Graphical abstract Image 1 Highlights • The nano-WC reinforcement is uniformly distributed in the TiAl matrix. • The average grain size is generally refined with the increase of nano-WC content. • The phase evolution mechanism of TiAl/WC nanocomposite is discussed in detail. • The TiAl/WC parts exhibit high strength and strain than traditional counterparts. [ABSTRACT FROM AUTHOR]

Abstract In this paper, the self-made MoS 2 nanosheets were attempted to be modified with oleic diethanolamide borate (ODAB) through a simple one-step route. The as-modified MoS 2 nanosheets were confirmed by a series of characterizations. The results showed that the MoS 2 nanosheets could be chemically well capped by ODAB to form C-S bonds. Furthermore, the tribological experimental results indicated that the ODAB-MoS 2 nanosheets as lubricant additives could improve the friction properties of base oil. At the optimal adding content of 0.06 wt%, the average friction coefficient, average wear scar diameter and extreme pressure performance of the ODAB-MoS 2 -based oil were decreased by about 27.9%, 22.9% and 17.4% as compared to base oil, respectively. Finally, the friction mechanism was discussed and proposed. Highlights • The MoS 2 nanosheets were chemically well capped by oleic diethanolamide borate molecules. • The ODAB-MoS 2 nanosheets possessed the better dispersibility and stability. • The ODAB-MoS 2 nanosheets showed better tribological properties. [ABSTRACT FROM AUTHOR]

Nanocomposite exchange coupled magnets are most likely the next-generation magnets because of their potentially high energy products. However, their corrosion resistance is a serious concern. The electrochemical behaviour of the nanocomposite magnets is largely unknown. In this study, we investigated the corrosion behaviours of α-Fe/Nd 2 Fe 14 B type nanocomposite magnets in a 3.5 wt% NaCl solution at room temperature using an electrochemical technique. Our results demonstrate that microstructure coarsening can improve the corrosion performance of the magnets, but it greatly degrades the magnetic properties. To enhance the corrosion resistance without scarifying the magnetic performance of the magnets, an amorphous phase with good corrosion resistance is introduced to the grain boundary of α-Fe/Nd 2 Fe 14 B type nanocomposite magnets by controlled melt-spinning process or adding Nb element. The nanocomposite magnets with an interfacial amorphous phase exhibit a lower corrosion current density (22.7 μA/cm 2 ) and higher maximum energy product (23 MGOe) than the magnets without an interfacial amorphous phase. These results indicate that the interfacial modification is beneficial to the improvement of both corrosion resistance and magnetic properties. [ABSTRACT FROM AUTHOR]

The purpose of this work was to investigate the feasibility of using sputtered Ti/W-Ti/Ti multilayer as diffusion barrier and buffer layers between β -Zn 4 Sb 3 thermoelectric (TE) material and Ag interconnect layer for mid-temperature TE module applications. Interdiffusion at the interface was examined by both scanning electron microscope and Auger electron spectroscopy. After penetrating the Ti buffer layer, Ag, Zn and Sb were successfully blocked by the W-Ti diffusion barrier layer. We also proved that the TE sample with diffusion barrier and buffer layers showed phase stability after high temperature aging. Also, the sheet resistance decreased as the temperature increased and it indicated good electrical properties at high working temperatures. In addition, the solid-liquid interdiffusion method was used to join the TE module, and the bonding remained stable at the TE module working temperature. [ABSTRACT FROM AUTHOR]

Intrinsic uniaxial stress along the [001] pc (pseudo-cubic [001]) direction in tetragonal PbZr 0.45 Ti 0.55 O 3 polycrystal is obtained via A-site acceptor-donor (Li + -Al 3+ ) co-doping. In-situ X-ray diffraction results demonstrate that local A-site cations ordering of donor-acceptor (along the [001] pc direction) should be responsible for the intrinsic uniaxial stress. The diffuse tetragonal-cubic phase transition and enhanced piezoelectricity are achieved in the doped ferroelectric. Based on the phenomenological theory, enhanced piezoelectricity is related to local low symmetry and stress-driven flattening of free-energy profile. The present study provides a promising method to obtain intrinsic uniaxial stress in Pb(TiZr)O 3 polycrystal via donor-acceptor co-doping, and reveal the relationship between this doping route, chemical stress and corresponding properties. [ABSTRACT FROM AUTHOR]

We have performed first-principles calculations to study the mechanical and thermodynamic properties of PuH 2 . The polycrystalline mechanical features, including various moduli, Poisson's ratio, Lame constants, Kleinman parameter, and hardness, are calculated according to the well-known Voigt-Reuss-Hill approximation. The results show that both ferromagnetic (FM) and antiferromagnetic (AFM) states are mechanically stable. Besides, we present the directional dependences of the Young's modulus as well as the shear modulus to investigate its mechanical anisotropy. The anharmonic properties of the AFM order is explored through computing the mode Grüneisen parameters. Employing the Slack theory, the temperature-dependent behavior of lattice thermal conductivity is obtained to analyze the thermal transportation ability in temperature range of 300–1000 K. [ABSTRACT FROM AUTHOR]

Composite C@NiCo 2 O 4 hollow microspheres (HSs) as electrode material were prepared via a two-step strategy of hard-template induced hydrothermal synthesis and calcination, in which SiO 2 @RF (resorcinol–formaldehyde resin, RF) sphere and hexamethylenetetramine (HMT) were used as hard template, and precipitant; Ni(NO 3 ) 2 ·6H 2 O and Co(NO 3 ) 2 ·6H 2 O as nickel and cobalt source, respectively. The resultant samples are characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), selected area electron diffraction (SAED) patterns, XPS and N 2 adsorption and desorption. The prepared C@NiCo 2 O 4 material possess large specific surface area of 127.61 m 2  g −1 and porous structure. The electrochemical measurements show that the C@NiCo 2 O 4 exhibit a large specific capacitance of 404 F g −1 at the current density of 1 A/g, a good cyclic stability with a capacitance retention of 87.1% after 1000 cycles of charge–discharge and a low resistance. [ABSTRACT FROM AUTHOR]

Micro- and nano-structured WC reinforced Co-based cladding layers on Ti 6Al 4V substrates were synthesized by laser cladding. The structure, phase composition, and wear behavior were investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), and friction-wear tests. High-angle annular dark field-energy dispersive spectroscopy (HAADF-EDS), transmission electron microscopy (TEM) and lattice images confirmed the XRD and SEM results. The interfaces exhibited good metallurgical bonding between the cladding layer and substrate owing to their high chemical affinity for each other. The cladding layer was composed of α(α′)-titanium, eutectics of CoTi 2 , β-titanium, TiC, eutectics of TiC TiB 2 , VC (Cr 3 C 2 ), (Ti, W)C 1− x , W, TiB 2 , and Co 3 W 3 C phases formed by the dissolution of WC. VC inhibited grain growth more effectively than Cr 3 C 2 or the combined effects of VC and Cr 3 C 2 . The wear resistance of the micro-/nano-WC cladding layers was markedly improved compared with those of Ti 6Al 4V. Nano-WC tended to convert into tungsten, however, the cladding layers easily became hard and brittle owing to aggregates of carbides or oxides. This effect resulted from interfacial boundaries formed by major differences at the α-Ti/α-Ti (Cr 3 C 2 , TiB 2 ) interfaces in terms of the chemical and structural contributions to the surface energy. [ABSTRACT FROM AUTHOR]

Cu-based composites are considered as one of the high performance and cost-effective materials to replace the noble metal-based electrical contact materials used in low-voltage electrical apparatus. However, the oxidation resistance of Cu-based electrical contact materials at high temperatures is still the major challenge that limits their applications. In this study, CuZr/Zn 2 SnO 4 composites were prepared through powder metallurgy method. The air arc erosion resistance of the composites under AC 380 V and 20 A was evaluated through the mass loss and the electrical contact resistance after experienced over 10,000 arc discharge cycles. The microstructure evolution, which reflected the deterioration process of the composites, was demonstrated through SEM analysis. The results indicated that the oxidation of Zr occurred along with the oxidation of Cu at high temperature, which considerably consumed the oxygen and thus significantly enhanced the oxidation resistance of Cu-based composites. In addition, TEM result showed a smooth and clear interface between Cu and Zn 2 SnO 4 phases, suggesting that the addition of Zn 2 SnO 4 phases was beneficial to enhance the durability of the composite. This work will not only merit the design and development of Cu-based electrical contact materials but also expand the applications of Cu-based composites in the air at high temperature. [ABSTRACT FROM AUTHOR]

A new type MoSi 2 /(Mo, Ti)Si 2 dual-phase composite coating for oxidation protection was designed and prepared on molybdenum alloy by a method of fused slurry. High temperature oxidation resistance of the coating has been investigated by isothermal oxidation test. Microstructure evolution and phase transformation of the as-prepared and oxidized coating were characterized. The results show that the composite coating is composed of primary C11 b MoSi 2 and C40 (Mo, Ti)Si 2 phases. The substitution of molybdenum with titanium in MoSi 2 gave (Mo,Ti)Si 2 of the C40 structure, resulting the formation of a C11 b MoSi 2 /C40 (Mo, Ti)Si 2 dual-phase composite coating. The composite coating could provide long term oxidation resistant protection for Mo alloy at high temperature, attributing to the good protection of a Si-Ti-O compound glass formation during oxidation. [ABSTRACT FROM AUTHOR]

The AlN/Y nanocomposite and nanomultilayered films with different Y contents were fabricated by the magnetron sputtering technique. The microstructures and mechanical properties of the AlN/Y nanocomposite and nanomultilayered films were characterized and measured, respectively. The AlN/Y nanocomposite film is composed of equiaxed AlN nanocrystallites encapsulated by the Y interfaces. When the Y:Al ratio is 2:23, Y interfaces can exist as the crystallized state and keep the epitaxial growth with the adjacent AlN nanocrystallites. Accordingly, the crystallization degree and mechanical properties are improved. The AlN/Y nanomultilayered film consists of the evident multilayered structure with distinct interfaces. When the Y-layer thickness is no more than 0.7 nm, Y layers are inclined to grow epitaxially with the adjacent AlN layers, leading to the improvement of crystallization degrees and mechanical properties. The interfacial evolutions and mechanical properties variations between AlN/Y nanocomposite and nanomultilayered films have the common feature as the Y content grows. It has been experimentally and theoretically verified that the AlN/Y nanocomposite and nanomultilayered films have the same coherent-interface strengthening mechanism. [ABSTRACT FROM AUTHOR]

The SiO 2 content had a significant influence on the microstructure, mechanical, thermal, and electrical properties of BaO-Al 2 O 3 -B 2 O 3 -SiO 2 glass-ceramics. The sintering kinetics suggested that the SiO 2 content changed the activation energy and affected the sintering process significantly. XRD analysis identified that with increasing SiO 2 content, the major crystal phase was changed from sanbornite to quartz and the minor phase cristobalite was precipitated. The change of vibrational modes detected by Raman spectrum was in accordance with the results of XRD. Owing to the variation of crystal phase content, the coefficient of thermal expansion was increased. Moreover, a modified model was established for calculating CTE values, which were consistent with experimental data. Meanwhile, the flexural strength and the Young's modulus remarkably increased from 67 to 150 MPa and 45–66 GPa, respectively. BABS glass-ceramic with 50 wt% SiO 2 showed excellent characteristics: σ = 150 MPa, E = 66 GPa, CTE = 13.37 × 10 −6 /°C, ε r = 6.0, tanδ = 6.4 × 10 −4 , indicating its potential for CBGA package. [ABSTRACT FROM AUTHOR]

We report n-type PbTe with a maximum ZT ∼1.2 at 673 K and an average ZT ave ∼0.84 at 300–823 K, which was achieved through a Sn and Se co-alloying approach. We find that the lattice thermal conductivity can be largely reduced through introducing Se in Te sites, and the power factor can be enhanced through introducing Sn in the Pb sites. Combining two strategies via Se and Sn co-alloying in PbTe, results show that the lattice thermal conductivity at 300 K can be reduced from ∼3.1 Wm −1 K −1 to ∼1.2 Wm −1 K −1 after alloying 15% Se, which is consistent with the Callaway model. Meanwhile, we find that both carrier concentration and mobility can be enhanced through alloying small amount of Sn, which are supported by DFT calculation with emphasis on the defect formation energies. The improvement on electrical conductivity elucidates an enhanced power factor at 300 K increasing from ∼6.4 μWcm −1 K −2 to ∼14.6 μWcm −1 K −2 . Through synergistically optimizing electrical and thermal transport properties of n-type PbTe via Sn and Se co-alloying, the ZT value is distinctly enhanced to 1.2 at 673 K, and the average ZT ave value is improved by ∼35%, from ∼0.62 in PbTe 0.997 I 0.003 to ∼0.84 in Pb 0.995 Sn 0.005 Te 0.847 Se 0.15 I 0.003 , ensuring a high maximum thermoelectric conversion efficiency ∼10.7%. [ABSTRACT FROM AUTHOR]

SnO 2 -based anode of lithium-ion batteries (LIB) suffers from excessive volume expansion and low conductivity, resulting in very poor capacity stability and rate capability. To solve the problems, three kinds of SnO 2 /Sn@carbon heterostructures were synthesized by a salt template following calcination using tartaric acid, p-phthalic acid and ethylenediamine tetraacetic acid with different carboxyl groups as carbon sources, respectively. The acidity, carbon atoms number and position affect the ratio of SnO 2 /Sn, the morphology and content of derived carbon, the advantage crystal plane and the surface defects of SnO 2. The carbon atoms located at carboxyl are transformed to CO and formed pores, and the carbon atoms at alkane chain are polycondensed and transformed to amorphous carbon during annealing process. The SnO 2 /Sn@C derived from tartaric acid (SnO 2 /Sn@TA) has the largest ratio of SnO 2 /Sn, which fixed on graphene-like porous carbon, exposed the most surface defects and more high energy crystal plane. The specific structure ensures structural stability and ultrahigh capacity, lower Li+ diffusion barrier energy and super rate capability. It exhibits the charge/discharge capacity of 1059.7/1064.4 mAh g−1 at 2 A g−1 after 1500 cycles and super rate performance of 399.3/404.5 mAh g−1 at 6 A g−1, which are superior to most reference data. [Display omitted] • Different heterostructures of SnO 2 /Sn@graphene-like porous carbon was synthesized. • C atoms at -COOH transform to CO to create pores, at alkane chain into amorphous C. • SnO 2 /Sn@C heterostructure decreases Li+ diffusion distance and barrier energy. • SnO 2 /Sn@C exhibits ultra-high capacity of 1064 mAh g−1 at 2 A g−1 for 1500 cycles. [ABSTRACT FROM AUTHOR]

Forming nanocomposites among different metal oxide species may lead to gas sensors with superior gas sensing properties. In this work, terbium oxide (Tb 2 O 3) was used to form composite nanofibers with zinc oxide (ZnO) to detect nitric oxide (NO) gas. The Tb 2 O 3 /ZnO composite nanofibers were synthesized through a facile electrospinning and annealing treatment. The heterostructure was investigated by various techniques such as XRD, SEM, TEM, and XPS, whereas the gas sensing performance of the composite nanofibers was investigated with a static gas testing system. Results showed that the Tb 2 O 3 /ZnO composite nanofiber exhibited excellent sensing performance to NO at 180 °C. Specifically, the composite nanofiber with [Tb]/[Zn] molar ratio of 0.01 had a high response of 28.3 (resistance ratio) to 1 ppm NO gas at 180 °C, with low response to other interference gases. The sensor also exhibited good repeatability and long-term stability. These remarkable sensing properties indicate that conventional ZnO is still promising for real applications via material composition and structure. • The Tb 2 O 3 /ZnO composite nanofibers can be synthesized through a facile electrospinning and annealing treatment. • The Tb 2 O 3 /ZnO composite nanofibers possess more abundant surface-adsorbed oxygen species than pure ZnO nanofibers. • The Tb 2 O 3 /ZnO composite nanofibers show better sensing properties than pure ZnO nanofibers. • The sensing mechanism of Tb 2 O 3 /ZnO composite nanofibers is related to the formation of p-n hetero-junction. [ABSTRACT FROM AUTHOR]

Study on structure-activity relationship between size and tribological properties of graphene oxide nanosheets(GO) in oil for the first time was presented. GO nanosheets with different size dimensions were prepared under different oxidation temperatures by using the improved Hummers method. The phase structure, size distribution and oxygen content of as-prepared GO nanosheets were determined by characterization techniques. The size dimension was tunable by controlling the oxidation temperature of the improved Hummers method. It was importantly revealed that the C/O ratio descended with the diminishing size of GO. The tribological properties of the resulting GO-based oils were intensively studied. Upon containing 0.04 wt% of GO content in oil, the GO-based oil exhibited the excellent antifriction and antiwear performance. More importantly, GO nanosheets with the smaller size and lower C/O ratio could significantly improve the tribological properties of oil. [ABSTRACT FROM AUTHOR]

Electronic structures modulation in MoS 2 /arsenene van der Waals (vdW) heterostructure with an external electric field (E ext ) are investigated by density functional theory (DFT). It is demonstrated that the MoS 2 /arsenene heterobilayer is a type-II vdW heterostructure, and therefore electrons and holes are spatially separated. The band gap of MoS 2 /arsenene is significantly modulated by E ext , eventually a transition from semiconductor to metal occurs. The positive and negative E ext have different effects on the band gap due to the spontaneous electric polarization in MoS 2 /arsenene heterostructure. The variation of band edges as a function of E ext provides further insight to the linear variation of the band gap. Furthermore, the MoS 2 /arsenene vdW heterostructure experiences transitions from type-II to type-I and then to type-II under various external electric fields. The E ext can control not only the amount of charge transfer but also the direction of charge transfer at the MoS 2 /arsenene interface. The present study would open a new avenue for application of ultrathin MoS 2 /arsenene heterojuction in future nano- and optoelectronics. [ABSTRACT FROM AUTHOR]

In this paper, a simple facile route for preparing zinc borate (ZB)/graphene oxide (GO) composites (ZB/GO) through a liquid phase-based ultrasonic-assisted stripping approach was demonstrated. As revealed by the FT-IR, XRD, Raman, UV–vis, TEM and SEM techniques, ZB hybrids were successfully composited with GO sheets. In order to highly disperse the composites into the base oil, the composites would be chemically modified in a reflux reaction with oleic diethanolamide (OD), i.e. OD-ZB/GO. The tribological properties of OD-ZB/GO as an additive in the base oil were tested by the four-ball wear machine. The results showed that the friction coefficient (COF) and the wear scar diameter (WSD) of the OD-ZB/GO-based oil (2.0 wt% of ZB/GO) were about 48.2% and 40.0% decline than those of the 500 SN base oil. Moreover, it could be found that the OD-ZB/GO-based oil showed a good carrying capacity at higher applied loads and an obviously reducing oil temperature performance in comparison of GO sheets and ZB hybrids. For proposing the wear mechanism, the as-prepared OD-ZB/GO in different viscosity base oil also was investigated intensively. The Raman spectra of wear surface revealed that the OD-ZB/GO materials entered the interfaces of motorial frictional pairs relied on base oil, thus displaying its antifriction and antiwear ability. [ABSTRACT FROM AUTHOR]

The Cu 2 ZnSnS 4 (CZTS) absorbers for thin film solar cells were fabricated by reactive sputtering followed by post-annealing. The effects of annealing temperature and Cu/(Zn + Sn) ratio on the film microstructure and related device performance were systematically investigated. It was found that the higher annealing temperature facilitates Zn incorporation and grains growth, but leads to more Sn loss and thicker MoS 2 layer. The CZTS absorbers with a lower Cu/(Zn + Sn) ratio show larger grain size and more ZnS particles on the surface, whereas the films with higher Cu content (Cu/Sn > 2) demonstrate small grain size, much Cu 2−x S phases and cracks. The highest device efficiency of 3.72% was obtained from the CZTS film annealed at 570 °C with Cu/(Zn + Sn) ratio of 0.78. The performance of devices is limited by low J sc and FF due to the interface recombination and the block of carrier transport by ZnS. [ABSTRACT FROM AUTHOR]

Microwave dielectric ceramics, with a Li 4+ x Ti 5 O 12 (0 ≤ x ≤ 1.2) formula, were prepared using a conventional solid-state reaction method. The effects of doping amount on the phase stability, microstructure and microwave dielectric properties were investigated. The XRD analysis showed that at x = 0, pure Li 4 Ti 5 O 12 could not be obtained but with trace amount of TiO 2 as a secondary phase, while single phase of the Li 4 Ti 5 O 12 solid solution was formed in x range of 0.2–0.4. The Li 4 Ti 5 O 12 and Li 2 TiO 3 coexisted in the compositions with 0.6 ≤ x ≤ 1.2 and the amount of Li 2 TiO 3 phase increased with increasing doping concentration. The microwave dielectric properties were strongly dependent on the sintering temperature and composition. A near-zero τ f of +2.7 ppm∕ ° C along with a Q × f of 36,000 GHz and a ε r of 25.1 was obtained in x = 1.2 sample sintered at 1000 °C. Moreover, promising low temperature co-fired ceramic (LTCC) materials with thermal stability and chemical compatibility with silver can be obtained in the x = 1.2 sample with 0.5 wt% B 2 O 3 addition sintered at 940 °C. This material has good microwave dielectric properties with ε r of 28.0, Q × f of 32,000 GHz and τ f of −7.8 ppm∕ ° C. [ABSTRACT FROM AUTHOR]

The SiCp/Mg-4Zn-0.5Ca composite was fabricated by semi-solid stirring assisted ultrasonic vibration and followed by ultra-slow-speed (0.01 mm s −1 ) extrusion at 280 °C. The results show that the as-extruded composite exhibits a typical bimodal microstructure consisted of ∼96.2% ultrafine dynamic recrystallization (DRXed) grains (∼0.86 μm) and relatively coarse unDRXed regions in a shape of elongated strips. Large amount of nanoscale MgZn 2 dynamically precipitated during ultra-slow-speed extrusion. The DRXed regions are thought propitious to the nucleation and growth of precipitate as compared with that of unDRXed regions. Compared with previous works on particle reinforced Mg matrix composites, the as-extruded SiCp/Mg-4Zn-0.5Ca composite not only possess high yield strength (322.7 MPa) and ultimate tensile strength (409.1 MPa), but also exhibit excellent ductility (10.1%). The ultrafine DRXed grains and large amount of dynamic precipitated nanoscale MgZn 2 are thought responsible for the superior strength of present composite. A typical linear hardening stage appears in the work hardening rate curve of as-extruded composite. Compared with the hinder effect of SiCp and dynamic precipitated nanoscale MgZn 2 on the movement of dislocations, the ultrafine DRXed grains play a main role on aggravating the dynamic recovery rate in stage Ⅲ. [ABSTRACT FROM AUTHOR]

In this work, disordered mesoporous polyacenes/sulfur (DM-PAs/S) composites with the S content of 50–80 wt % were prepared via a simple melt-diffusion strategy. In order to obtain such DM-PAs/S composites, the non-sulfur-containing disordered mesoporous polyacenes (DM-PAs) precursor, which had a high BET surface area of 1136.0 m 2 /g, a pore volume of 1.37 cm 3 /g and unique bimodal mesopores (2.98/7.39 nm), was firstly prepared by using phenol-formaldehyde (PF) resin as raw material as well as both polyethylene glycol (PEG) and ZnCl 2 as activation agents. Electrochemical tests demonstrated that, the as-prepared DM-PAs/S could be served as superior cathode materials for lithium-sulfur batteries. It was disclosed that the DM-PAs/S with the S content of about 67 wt % (S-DM-PAs/S-67) presented the best electrochemical properties when the specific capacity is calculated based on the total mass of DM-PAs/S composite containing active sulfur and inactive DM-PAs. At a charge/discharge rate of 1 C, the S-DM-PAs/S-67 electrode exhibits a good long-term cycling stability with a high reversible capacity of about 513.57 mAh/g Sulfur after 500 cycles. The advanced electrochemical performances should be attributed to the uniform distribution of sulfur in the DM-PAs matrix, high electronic conductivity of DM-PAs, and the effective hinder of dissolvable polysulfides by the pores in the DM-PAs. [ABSTRACT FROM AUTHOR]

La 0.75 Mg 0.25 Ni 3.2−x Co 0.2 Al 0.1 Mo x (x = 0, 0.10, 0.15, 0.20) hydrogen storage alloys were synthesized via vacuum induction melting combined with a heat-treatment at 1173 K for 8 h. All alloys have multiphase constitutions including (La, Mg) 2 Ni 7 , (La, Mg) 5 Ni 19 , LaNi 5 phase and there is residual Mo phase in the Mo-added alloys. Increasing Mo content, the abundance of (La, Mg) 2 Ni 7 and (La, Mg) 5 Ni 19 phase with super-lattice stacking structure initially increases and then decreases while that of LaNi 5 phase shares a reverse trend. In all Mo-added alloys, Ni is partially substituted by Mo leading to an overall expansion in unit cell volumes. The electrochemical analyses show that the cyclic stability of the alloy electrodes are significantly improved after Mo is added especially when x = 0.15 the cyclic retention is 80.9%, which is 16.4% higher than that of the original one. The maximum discharge capacity are almost unchanged between the alloy electrodes for x = 0 and x = 0.15 while the high-rate discharge ability at the discharge current density of 1500 mA/g is enhanced from 55.2% to 60.1%. The comprehensive electrochemical properties reach a compromise for La 0.75 Mg 0.25 Ni 3.05 Co 0.20 Al 0.10 Mo 0.15 alloy electrode which possesses remarkably improved cyclic stability, enhanced kinetic property and maintains almost unimpaired discharge capacity in the meanwhile. [ABSTRACT FROM AUTHOR]

A series of TiN/Ni nanocomposite films with different Ni content were synthesized by reactive magnetron sputtering. The microstructural evolution, mechanical properties and strengthening mechanism of TiN/Ni nanocomposite film were studied. When Ni:Ti ratio is less than 1:24, the small amount of Ni can be dissolved in the TiN matrix, leading to the slight decrease of the hardness and elastic modulus. When Ni:Ti ratio rises to 4:21, Ni inclines to separate from TiN due to the thermodynamic incompatibility as an interfacial phase and grow coherently with adjacent TiN crystallites. As a result, the TiN/Ni film was remarkably strengthened with the maximal hardness and elastic modulus of 33.3 GPa and 373 GPa. As Ni:Ti ratio further increases to 5:20, Ni interface transforms into amorphous state, leading to the destruction of the epitaxial growth structure and the rapid decrease of hardness and elastic modulus. The strengthening effect of TiN/Ni nanocomposite film can be attributed to the coherent interface between Ni interfacial layers and TiN crystallites. [ABSTRACT FROM AUTHOR]

Herein, sandwich-like Ti 3 C 2 T x MXene/SnO 2 quantum dots composites were synthesized as sulfur host, aiming to alleviate the shuttle effect of polysulfides present in lithium-sulfur batteries. SnO 2 quantum dots (SnO 2 QDs) were introduced into the interlayer of MXene through a simple electrostatic self-assembly method, and the mass fraction of SnO 2 QDs was controlled to construct sandwich MXene/SnO 2 QDs. While SnO 2 QDs effectively alleviating the stacking tendency of MXene, Ti and Sn co-chemisorb polysulfides and the interlayer structure physically confines polysulfides. Significantly, the synergistic effect between MXene with SnO 2 QDs effectively alleviates the shuttle effect of polysulfides and buffers the volume expansion. Meanwhile, with the help of the catalysis of SnO 2 QDs, the liquid-solid reaction kinetics of lithium polysulfides converting to Li 2 S 2 /Li 2 S is accelerated. Electrochemical test results showed that the MXene/SnO 2 QDs/S cathode has a high initial discharge specific capacity (1147.6 mAh g−1 at 0.1 C, while MXene/S is only 615.4 mAh g−1), as well as excellent rate performance and cycling stability in Li-S batteries. • Sandwich-like Ti 3 C 2 T x MXene/SnO 2 QDs composites were successfully synthesized as sulfur host in lithium-sulfur batteries. • The Ti 3 C 2 T x /SnO 2 QDs effectively alleviates the shuttle effect of polysulfides and buffers the volume expansion. • The MSn/S has a high initial discharge specific capacity (1147.6 mAh g−1 at 0.1 C, while MXene/S is only 615.4 mAh g−1). [ABSTRACT FROM AUTHOR]

Transition metal phosphides are considered as promising alternatives to noble-metal based electrocatalysts for water splitting due to their bifunctional catalytic activity. The modulation of morphology and electronic structure is an efficient strategy to improve the mass transport and electronic conductivity of metal phosphides, but still faces a great challenge to achieve this conjoint regulation. Herein, a facile Zn-doped strategy was developed to synthesize cobalt phosphide (CoP) catalyst with thickness-controlled porous nanosheet structure. At the current density of 10 mA cm−2, the optimized Zn 0.1 -CoP catalyst delivers an overpotentials of 290 mV and 98 mV for OER and HER, respectively. The cell voltage for the overall water splitting is 1.57 V to reach the current density of 10 mA cm−2, outperforming the counterparts of noble metal-based Pt/C and IrO 2 catalysts. The density functional theory (DFT) calculations reveal that Zn doping can effectively improve the conductivity and regulate the electronic structure of CoP, thus resulting in fast charge transfer transport and reduced energy barrier of the rate-determining step. This work provides a favorable strategy for the rational design of bifunctional catalysts with high-performance for overall water splitting. [Display omitted] • The Zn-doped CoP electrocatalysts with controllable morphology and electronic structure have been facilely synthesized • Zn-doped CoP porous nanosheets and its in -situ transformed Zn-CoOOH exhibit enhanced catalytic properties • The electronic structure and intrinsic catalytic activity of CoP can be finely regulated by Zn doping • The designed Zn 0.1 -CoP catalyst shows superior water-splitting performance to the commercial Pt/C-IrO 2 catalysts [ABSTRACT FROM AUTHOR]

Single phase multiferroics are rare in nature, because ferroelectric and ferromagnetic orderings require empty d -orbits and filled d -orbits, respectively. Here we demonstrate that ferroelectricity can be induced by ion-pair doping in ferromagnetic oxide such as ferrites with filled d -orbits. Our study shows that a new kind of room temperature multiferroic can be achieved in single phase thin films of CoFe 2 O 4 with Li + -Al 3+ pair substitution of Co 2+ along 〈110〉 direction. A ferroelectric domain mechanism related to ion-pairs in co-doped thin films was revealed. Importantly, a new way for fabricating single phase multiferroic materials is provided in the present study. [ABSTRACT FROM AUTHOR]

(Ba 0.99 Ca 0.01 )(Ti 0.98 Zr 0.02 )O 3 (BCZT) and Pr-doped samples (Pr 0.002 Ba 0.988 Ca 0.01 )(Ti 0.98 Zr 0.02 )O 3 (BCZT-A) as well as 0.998(Ba 0.99 Ca 0.01 )(Ti 0.98 Zr 0.02 )O 3 -0.002PrO 1.5 (BCZT-W) lead-free piezoelectric ceramics were prepared by conventional solid state reaction method. The structural, dielectric, piezoelectric, ferroelectric and luminescence properties of the Pr-doped BCZT ceramics were systematically studied. The orthorhombic-tetragonal (O–T) phase transition temperature decreased obviously, while Curie temperature ( T C ) maintained at 118 °C for both of the Pr-doped BCZT ceramics. The BCZT-A ceramics exhibited the best piezoelectric properties ( d 33 = 344 pC/N) and ferroelectric properties ( P r = 13.042 μC/cm 2 ). Meanwhile, desired luminescence properties (bright reddish-orange light, emission peak centered at 649 nm) were obtained under an excitation of 448 nm at room temperature for BCZT-A and BCZT-W ceramics. The luminescence properties of the BCZT-A ceramics were better than those of the BCZT-W ceramics. Asymmetric structure, coexistence of orthorhombic and tetragonal phases at room temperature and less oxygen vacancies exhibited in BCZT-A ceramics could result in the improved piezoelectric properties and luminescence properties simultaneously. These results suggest that the BCZT-A ceramics have potential application as a multifunctional device by integrating its excellent electrical and luminescence properties. [ABSTRACT FROM AUTHOR]

This work presents a comprehensive study on the laser scanning speed on the microstructure development, phase evolution and nanohardness of a TiAl alloy, Ti-45Al-2Cr-5Nb (at.%), processed by selective laser melting (SLM). The experimental results show that when increasing the laser scanning speed from 500 to 800 mm/s, the average grains size decreases from 7.11 μm to 5.43 μm, whereas the crystallographic texture showing a combination of (0001), ( 10 1 ¯ 1 ) and ( 11 2 ¯ 1 ) orientations basically remains unchanged. The SLM-processed TiAl alloy is dominated by high-angle (>15°) grain boundaries (HAGBs) and the contents of HAGBs decrease from 91.6% to 86.1% when the laser scanning speed varies from 500 to 800 mm/s. The α 2 phase decreases while the γ and B 2 phases increase with increasing the laser scanning speed. Moreover, the phase evolution mechanism in the SLM-processed TiAl alloy can be described as follows: (200) β transforms to ( 20 2 ¯ 0 ) α 2 and (110) γ , and then the residual B 2 and the incompletely transformed γ phase randomly distributed in the α 2 phase matrix. The nanohardness of the SLM-process TiAl alloy increases from 7.90 ± 0.32 GPa to 9.49 ± 0.46 GPa with increasing laser scanning speed from 500 to 800 mm/s, which is much higher than those of traditionally manufactured counterparts, such as casting parts (4.98 ± 0.10 GPa) and TiB 2 reinforced TiAl alloy fabricated by roll bonding (6.73 GPa). With the increase of laser scanning speed from 500 to 800 mm/s, compression properties of the SLM-process TiAl alloy increases from 829.41 ± 24.88 MPa to 1216.16 ± 36.48 MPa. [ABSTRACT FROM AUTHOR]

FeNiCoAlTaB alloy with good superelasticity was fabricated by using the directional solidification technology to control grain orientation and solution-aging treatment to change the morphology and distribution of precipitates, and the superelasticity improving mechanism of the alloy was investigated in this study. The results indicated that with the melt zone temperature of 1420 ± 5 °C and withdrawing velocity of 0.5 mm/min, the columnar-grained FeNiCoAlTaB alloy with strong 〈100〉 fiber texture was obtained. After solution treatment at 1315 °C for 20 min and aging at 700 °C for 6 h, the columnar-grained FeNiCoAlTaB alloy exhibited the superelasticity strain of 1.7%, residual strain of 0.5% and tensile strength of 860 MPa. Compared with the non-superelastic equiaxed-grained alloy fabricated by vacuum melting and forging, the desired grain orientation, the size and distribution of the precipitates resulted in the good superelasticity of the columnar-grained FeNiCoAlTaB alloy. [ABSTRACT FROM AUTHOR]

Ultrasonic surface rolling processing (USRP) was performed on a Mg–Y–Nd–Zr alloy after equal-channel angular pressing. The result shown that the surface roughness was significantly improved, residual stress was introduced to the topmost surface, and ~450 µm gradient nanostructure (GNS) of Mg alloys was obtained after USRP treatment. The mechanism of microstructure evolution and its effect on the mechanical properties of the Mg alloy were studied in detail. There are multiple deformation mechanisms in grain refinement. In the initial stage, the coarse-grain (CG) matrix was subdivided by {10 1 ̅ 2}< 10 1 ̅ 1 > extension twins. Subsequently, the deformed grains were refined into substructures using interaction between twins, interaction between twins and dislocations, and dislocation entanglement. Moreover, the substructure contains a high density of multiple stacking faults and dislocation arrays, which can effectively block dislocation movement and promote dislocation packing. Finally, equiaxed nanograins (NGs) with high-angle grain boundaries were formed via subcrystal rotation recrystallization. With the formation of a GNS, the strength of the Mg–Y–Nd–Zr alloy considerably increased at the expense of a small amount of plasticity. The tensile test results demonstrated that the yield strength (YS) and ultimate tensile strength (UTS) of the Mg–Y–Nd–Zr alloy increased from 171.96 and 262.47 MPa to 216.06 and 330.61 MPa, respectively, and the elongation rate decreased from 20.52% to 14.65% after the USRP treatment. The YS improvement of the Mg–Y–Nd–Zr alloy after the USRP treatment was attributed to grain boundary strengthening, synergistic strengthening, dislocation strengthening, and twin strengthening. Furthermore, the microhardness of Mg–Y–Nd–Zr considerably improved after USRP treatment, and grain refinement was the primary surface strengthening mechanism of the Mg–Y – Nd – Zr alloy after the USRP treatment. The work-hardening capacity of the Mg alloy improved after the USRP treatment, and the synergistic deformation between GNS and CG matrix was the primary reason for the excellent work-hardening capacity of the Mg–Y–Nd–Zr alloy. • The gradient nanostructure of Mg alloys was obtained by ultrasonic surface rolling processing. • The microstructure evolution mechanism of Mg alloys during ultrasonic surface rolling processing was discussed in detail. • The surface strengthening mechanism of Mg alloys after ultrasonic surface rolling processing was discussed in detail. [ABSTRACT FROM AUTHOR]

Mn 4+ /Tm 3+ co-doped Ca 14 Zn 6 Al 10 O 35 near infrared phosphor is prepared with a sol–gel method and intense 1.85 μm emission of Tm 3+ sensitized by Mn 4+ is observed for the first time. The intense and broad excitation band of Mn 4+ (250–550 nm) and efficient Mn 4+ → Tm 3+ energy transfer make the 1.85 μm emission very convenient to be obtained by pumping with light in a wide-wavelength region, especially with commercial GaN LEDs. The mechanisms for the Mn 4+ → Tm 3+ and Tm 3+ –Tm 3+ interaction have been discussed based on the Mn 4+ and Tm 3+ concentration dependent steady-state and transient spectral properties. It is found that both the Mn 4+ → Tm 3+ sensitization and the Tm 3+ –Tm 3+ inter-action are helpful to the improvement of the near infrared luminescence, resulting in the 1.85 μm emission for the Mn 4+ /Tm 3+ co-doped phosphor 24 times of enhancement under excitation of 455 nm light as compared with that for the Mn 4+ absent sample. [ABSTRACT FROM AUTHOR]

Plate-like LiFePO 4 /C composite with preferential (010) lattice plane is successfully prepared via cetyltrimethylammonium bromide (CTAB)-assisted in-situ hydrothermal carbonization synthesis. The structure, morphology and electrochemical property of the as-obtained products are studied by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution trans mission electron microscopy (HRTEM) and galvanostatic charge–discharge test, respectively. Due to the synergism of uniform carbon coating enhancing transfer efficiency of electrons and preferential growth of (010) lattice plane facilitating diffusion of Li-ions, the LiFePO 4 /C composite shows excellent electrochemical performance. The as-obtained products deliver high-rate capacities of 125 mAh g −1 at 10 C and 110 mAh g −1 at 20 C, while preserving a high tap density of 1.3 g cm −3 . [ABSTRACT FROM AUTHOR]

In this study, the phase evolution, microstructure and magnetic properties of bulk α-Fe/Nd 2 Fe 14 B nanocomposite magnets prepared by a combination of severe plastic deformation (SPD) and thermal annealing have been investigated. Experimental results demonstrate that SPD affects the phase evolution of (Nd,Pr)-Fe-Co-Nb-B alloy upon annealing significantly. The formation of metastable intermediate phases, such as Nd 2 Fe 23 B 3 and Fe 3 B, in the alloy has been effectively inhibited as the strain ε is increased to ε = 6.1, yielding a high volume fraction of α-Fe phase ( V c ∼ 37%) in the bulk α-Fe/Nd 2 Fe 14 B magnets. The grain size of α-Fe and Nd 2 Fe 14 B phases in the magnets decreases with increasing strain. A smaller grain size d = 13.3 nm for α-Fe and 26.5 nm for Nd 2 Fe 14 B is achieved at ε = 6.1, and the magnets show the magnetic properties, ( BH ) max = 14.9 MGOe and H c = 6.4 kOe, larger than those in the α-Fe/Nd 2 Fe 14 B magnets made by directly annealing amorphous ribbons, ( BH ) max = 10.3 MGOe and H c = 4.6 kOe. The enhanced coercivity in the SPD magnets results from an increase in domain-wall-pinning strength. [ABSTRACT FROM AUTHOR]

Through introducing the CrAlSiN modulation layers consisted of CrAlN and SiN x phases, a series of TiN/CrAlSiN nanomultilayered films with different Si content were synthesized by reactive magnetron sputtering. The effect of Si content on microstructural evolution and superhardness effect of TiN/CrAlSiN nanomultilayered film was investigated by XRD, HRTEM and nanoindentation techniques. When inserted by CrAlSiN nano-layers with Si:CrAl ratio less than 4:21, TiN layers can force CrAlSiN layers to transform into fcc structure and grow epitaxially with them, leading to appearance of the superhardness effect. The columnar crystal structure of TiN/CrAlSiN nanomultilayered film can be effectively refined by insertion of the CrAlSiN layers due to thermodynamic incompatibility of CrAlN and SiN x . As the Si content further increases, the amount of amorphous SiN x phase increases, which makes the CrAlSiN layers present amorphous feature and blocks the epitaxial growth structure within the TiN/CrAlSiN nanomultilayered film, resulting in the decrease of hardness and elastic modulus. [ABSTRACT FROM AUTHOR]

The NiCr/Al nanomultilayered films with different Al thicknesses (t Al) were prepared by magnetron sputtering. The structural evolution of the Al nanolayer with the increase in t Al was investigated. When the Al layer thickness changed from 1.2 nm to 2.4 nm, the Al layer could keep the co-epitaxial growth with the adjacent NiCr layer. Accordingly, the crystallization degree improved. When the Al layer thickness changed from 2.4 nm to 3.0 nm, the transformation from the coherent to incoherent interfaces took place between the NiCr and Al layers. Meanwhile, the co-epitaxial growth with the adjacent NiCr nanocrystallites was destroyed, the crystallinity and the grain size decreased, leading to the increase of the resistivity under the combined effects of the grain boundary scattering and interface scattering. The interfacial evolution of NiCr/Al nanomultilayered films was closely related to the changes of electrical properties. When the Al layer thickness changed from 3.0 nm to 3.6 nm, the surface quality of the film was improved, which effectively reduced the scattering of defects and vacancies during the electron transport, resulting in the decrease of the resistivity of the NiCr/Al nanomultilayered film. [Display omitted] • Al films inserted NiCr nanolayers with different thickness were synthesized. • The microstructure structure of NiCr was damaged with insertion of Al nanolayers. • The resistivity was renewedly increased with the change of interface structure. • The resistivity later deteriorates with the improvement of the surface quality. [ABSTRACT FROM AUTHOR]

Elemental powders of nanosized tungsten and chemically deposited nanosized copper were used for preparing tungsten/copper composites, which are used as electric contact components. A composite of 70 wt.%W/30 wt.%Cu (52 vol%W/48 vol%Cu) composition was prepared by three powder metallurgy techniques. Elemental mixing, mechanical milling and electroless Cu coating on tungsten particles were used for the synthesis. The obtained powder blends underwent consolidation by rapid hot pressing using the spark plasma sintering (SPS) route at 950 °C under vacuum and by conventional vacuum pressureless sintering for comparison. The elemental powders and the sintered composites were investigated by optical microscopy and SEM. Electrical conductivity, hardness, transverse rupture strength, and wear properties were measured. Results show that the synthesis of the composite by the investigated route yields good performance. Samples prepared by SPS have shown better mechanical properties than those prepared by compaction and sintering due to their fine microstructure. [ABSTRACT FROM AUTHOR]

Analysis of ZnS segregation behaviour and its influence on the device performance has been made on the Zn-rich Cu 2 ZnSnS 4 thin film solar cells. Cross-sectional transmission electron microscopy images reveal that ZnS is the main secondary phase in the Cu 2 ZnSnS 4 layer obtained from a sulphurised Zn/CuSn metallic stack. The excess Zn diffuses from back contact region to top surface of Cu 2 ZnSnS 4 layer accumulating in the form of ZnS. The solar cell with a higher Zn concentration shows a large quantity of isolated ZnS grains at Cu 2 ZnSnS 4 top surface which is close to CdS/Cu 2 ZnSnS 4 heterojunction interface. Soft X-ray absorption spectroscopy indicates a large spike-like conduction band offset between Cu 2 ZnSnS 4 and ZnS. Consequently, such much ZnS precipitates would increase series resistance and generate lower short-circuit current and external quantum efficiency. However, appropriate amount of ZnS at the space charge region of the solar cell has beneficial effects by reducing the heterojunction interface recombination. Therefore, an improved open-circuit voltage and a higher shunt resistance are achieved. This paper provides a possible method to intentionally segregate ZnS at the space charge region by depositing the Zn layer at the bottom of co-sputtered CuSn layer. Although it is difficult to synthesis a pure phase Cu 2 ZnSnS 4 absorber, we can utilise the ZnS secondary phase to improve the Cu 2 ZnSnS 4 solar performance by controlling the Zn-excess amount. [ABSTRACT FROM AUTHOR]

Recently, Ag incorporation into Cu(In,Ga)Se 2 structure was found to benefit the solar cell performance. However, (Ag,Cu) 2 ZnSnS 4 used as the solar cell absorber is not widely reported even though Ag 2 ZnSnS 4 has shown much better photocatalysts activity for H 2 evolution than Cu 2 ZnSnS 4 . In this paper, (Ag,Cu) 2 ZnSnS 4 thin film solar cell was synthesized through sulfurization of Ag/Zn/Cu/Sn metallic stacked layers. In order to understand the actual role of Ag in the Cu 2 ZnSnS 4 structure, the changing chemical environment, microstructure and intragrain defect due to the Ag incorporation, were studied by X-ray photoelectron spectroscopy and transmission electron microscopy. After sulfurization, Ag is uniformly distributed in the absorber and is incorporated into Cu 2 ZnSnS 4 crystal structure but no obvious change of the Cu 2 ZnSnS 4 chemical environment is detected. A large density of voids is formed at the Cu 2 ZnSnS 4 /Mo interface and some of these voids are found to be coated with CdS which is believed to be detrimental to Cu 2 ZnSnS 4 device performance. In contrast, Ag incorporation reduces the size and amount of voids and thus effectively eliminates CdS deposited at back contact region. Moreover, fewer planar defects and Cu vacancies are formed in the (Ag,Cu) 2 ZnSnS 4 sample than Cu 2 ZnSnS 4 sample as suggested by electron diffraction patterns. Therefore, improved solar cell performance should result from the formation of (Ag,Cu) 2 ZnSnS 4 structure. [ABSTRACT FROM AUTHOR]

Ge-substituted Cu 2 ZnSnS 4 (CZTS) thin films are promising for solar cell manufacturing, especially for graded-band-gap solar cells and multi-junction solar cells. However, there is no systematic research on the change of structural properties of Cu 2 Zn(Ge x Sn 1 − x )S 4 (CZTGS) as the function of alloy composition x . In this work, polycrystalline CZTGS thin films were prepared by sulfurizing sputtered Zn/Cu/Ge/Sn metallic precursor stacks. Energy-dispersive X-ray spectroscopy (EDS) line scans conducted in a transmission electron microscopy (TEM) system shows uniform element distribution (except of some ZnS segregation) throughout the synthesized films. The analysis of X-ray diffraction (XRD) and Raman spectroscopy confirms that Cu 2 ZnGeS 4 is successfully obtained by sulfurizing metallic stacks at 580 °C for 2 h. The lattice constants a and c of CZTGS as derived from XRD patterns follow the Vegard’s rule that lattice constants vary linearly with Ge content ( x ). Raman spectra shows an A1 mode shift towards high frequency when Sn is gradually replaced by Ge. Chemical composition study indicates the increase in x value leads to higher (Ge + Sn) element loss during the sulfurization process, which can be explained by the high vapour pressure of Ge sulfides. By alloying with Ge, the grain size of CZTS is enlarged which also leads to a rough surface. [ABSTRACT FROM AUTHOR]

• MoS 2 containing crystal water is synthesized by a simple hydrothermal method. • The electrochemical performance of the MoS 2 with/without crystal water are tested to further understand the role of crystal water in MoS 2. • Due to the lubrication and support of crystalline water, the MoS 2 ·nH 2 O electrode delivers a high specific capacity and satisfactory cyclability. • The polarization resistance change of MoS 2 ·nH 2 O and MoS 2 -400 in the aqueous zinc ion batteries was calculated through the DRTtoolbox in MATLAB. MoS 2 ·nH 2 O was synthesized by a simple hydrothermal method, and the unique nanoscale flower structure combined with the lubricating effect of crystal water make it exhibit good capacity and stability in aqueous Zn2+ ion batteries. [Display omitted] As a special group of two-dimensional layered compounds, transition metal dichalcogenides (TMDs) have attracted great attentionfor rechargeable zinc ion batteries (ZIBs). However, the large zinc ion radius, the strong electrostatic interaction with the host material, and the slow dynamics of Zn2+ limit the application of TMDs in rechargeable aqueous ZIBs. Herein, MoS 2 ·nH 2 O is synthesized through a facile hydrothermal reaction. The unique nanoscale flower structure combined with the introduction of crystal water can reduce the electrostatic interaction between zinc ion and skeleton, promote the diffusion of zinc ion, and effectively accelerate the reaction kinetics. Benefiting from the above advantages, the MoS 2 ·nH 2 O electrode exhibits a high rate capacity and satisfactory cyclability (88% capacity retention after 800 cycles at 2 A g−1). The excellent performance of MoS 2 ·nH 2 O proves that the introduction of crystal water is a practical strategy to promote the hydration kinetics of large-size multivalent ions, which may provide a viable and attractive solution for the synthesis of other cathode materials for aqueous ZIBs. [ABSTRACT FROM AUTHOR]

An innovative approach to improve the quality of TiC-TiSi 2 -Al 2 O 3 composite coating was demonstrated. In-situ synthesis is one of the most economical methods for preparing refractory composite coatings, but the problems of low reaction degree and poor quality of the as-prepared coatings still exist. In the present investigation, TiC-TiSi 2 -Al 2 O 3 , Al-TiO 2 -SiC and heat-treated Al-TiO 2 -SiC composite powders were plasma sprayed on the surface of TC4 titanium alloy to prepare TiC-TiSi 2 -Al 2 O 3 composite coatings, respectively. The phase composition and microstructure of the three kinds of composite powders and as-prepared coatings were analyzed, and the porosity, microhardness and fracture toughness of the coatings obtained by the three kinds of composite powders were comparatively studied. The results show that the heat-treated Al-TiO 2 -SiC composite powders had higher density and smoother surface than that of Al-TiO 2 -SiC composite powders. The pre heat treatment of Al-TiO 2 -SiC feedstock could avoid the inadequate reaction during the plasma spraying process. The coating obtained by plasma spraying heat-treated Al-TiO 2 -SiC composite powders had the highest bonding strength, microhardness (51.8% higher than Al-TiO 2 -SiC coating) and fracture toughness among the three coatings. • Density and cohesive strength of Al-TiO 2 -SiC powder were improved by heat treatment. • Al-TiO 2 -SiC powders were plasma sprayed to prepare TiC-TiSi 2 -Al 2 O 3 composite coatings. • Coating obtained by heat-treated Al-TiO 2 -SiC powder had higher hardness and toughness. [ABSTRACT FROM AUTHOR]

A cathode material carbon-coated Na 2 FePO 4 F (Na 2 FePO 4 F@C) was reported which were derivated from waste biomass bagasse as carbon source were prepared by wet ball milling and in-situ pyrolysis, due to the low cost and easy availability of biomass carbon materials. The performance results shown that the Na 2 FePO 4 F@C composite material prepared under the condition of 10% carbon source and calcination temperature of 650 °C crystallized well, and the carbon material was coated on the external of Na 2 FePO 4 F well with no damaging the crystal structure of the material. The first ring discharging specific capacity with Na 2 FePO 4 F@C was 128 mA h g−1 based on 0.1 C current density, which was a three-fold increase compared with the carbon-free coated material Na 2 FePO 4 F (40 mA h g−1). The coulomb efficiency of Na 2 FePO 4 F@C cathode material remained above 97.8% after 30 cycles at 0.1 C. This work applied biomass carbon materials to hybrid ion batteries, offering more possibilities for the development of sodium-based fluorophosphate materials for lithium-ion batteries coated with low-cost biomass-based carbon materials. • Na 2 FePO 4 F/C cathode materials were prepared and characterized. • The prepared cathode material was assembled into a button battery. • The coulomb efficiency of Na 2 FePO 4 F/C cathode material was 97.8% after 30 cycles. [ABSTRACT FROM AUTHOR]

The (AlCrTiZrHf)N high-entropy alloy nitride films were synthesized by reactive magnetron sputtering. The effects of different N 2 flow rates on the microstructures and mechanical properties of (AlCrTiZrHf)N films were studied by the X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), nanoindentation, coating friction and wear tester. The results show that the AlCrTiZrHf high-entropy alloy film presents an amorphous state. With the increase of the N 2 flow rate, the (AlCrTiZrHf)N high-entropy alloy nitride films transform to a face-centered-cubic (FCC) structure. When the N 2 :Ar ratio is 5:4, the hardness and elastic modulus of the films reach 33.1 GPa and 347.3 GPa, respectively. The strengthening effect is mainly attributed to the formation of saturated metal-nitride phases and the solid-solution strengthening of various elements. Meanwhile, the (AlCrTiZrHf)N film exhibits the low friction coefficient and superior wear resistance. Based on the excellent properties of high-entropy alloy nitride films, the (AlCrTiZrHf)N film presents a potential application in protective coating. Image 1 • The (AlCrTiZrHf)N high-entropy alloy nitride films with different nitrogen content were produced. • The (AlCrTiZrHf)N films transform to a face-centered-cubic (FCC) structure with the increase of the N 2 flow rate. • When the N 2 :Ar ratio is 5:4, the hardness and elastic modulus of the film reach the maximum of 33.1 GPa and 347. • GPa.4.The friction coefficient was 0.5. [ABSTRACT FROM AUTHOR]

ZIF-8@TiO 2 micron composite, one kind of new high-efficiency photocatalyst was prepared by hydrothermal method in this work. We compared the ability of ZIF-8, TiO 2 nanospheres and ZIF-8@TiO 2 to catalytically degrade tetracycline. The results of the characterization show that the TiO 2 nanospheres grow uniformly on the surface of ZIF-8, and ZIF-8 and TiO 2 are linked together by chemical bonds. The synergistic effect of ZIF-8 and TiO 2 greatly enhances the catalytic ability of the composite photocatalyst. In ZIF-8@TiO 2 micron composite, ZIF-8 provides a new way for photogenerated electron transfer as a charge separator, to reduce the charge recombination rate. Since the hybrid combines the advantages of ZIF-8 and TiO 2, ZIF-8@TiO 2 exhibits excellent ability to catalytically degrade tetracycline. The possible photocatalytic mechanism of the hybrid photocatalyst was also discussed. Image 1 • ZIF-8@TiO 2 core-shell micron composite exhibits excellent photocatalytic ability and adsorption capacity. • Synergistic effect of ZIF-8 and TiO 2 can improve the photodegradation efficiency of tetracycline. • •O 2 − is the most effective active species in the mechanism for TC degradation. [ABSTRACT FROM AUTHOR]